Optical switcher used for broadcast station

ABSTRACT

To provide an optical switcher capable of sending incident light on one input port to any plurality of output ports. The optical switcher includes input ports disposed on extensions of m input optical paths (m being 2 or greater natural number), output ports disposed on extensions of n output optical paths (n being 2 or greater natural number), and movable translucent switch mirrors  3   11 - 3   mn , disposed at intersections of the m input optical paths and the n output optical paths, for switching between the input optical paths and the output optical paths. A switch mirror  3   11 - 3   mn  located nearer the input ports has a higher transmittance.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optical switcher used in asignal transmission/distribution system or the like used in a broadcaststation.

[0003] 2. Description of the Related Art

[0004] In the past, optical switchers having a plurality of inputs andoutputs have been developed for cross connection in a trunk transmissionnetwork. In general, cross connection in the trunk transmission networkis only required to implement a N-to-N nonblocking switching, and is notrequired to implement a one-to-N broadcasting mode connection. To thecontrary, switchers used in a broadcast station or the like are requiredto have a capability of signal distribution, and thus, the one-to-Nbroadcasting mode connection is required. Conventionally, only switchingof an uncompressed SDTV (Standard Definition Television) serial digitalsignal transferred at a rate of 270 Mb/s at most was needed, and thus,the one-to-N broadcasting mode connection could be readily realizedelectrically by electrical switchers.

[0005] Recently, broadcast stations have been required to transmit andswitch an uncompressed HDTV (High Definition Television) serial digitalsignal at a transfer rate of 1.5 Gb/s. In order to transmit the serialdigital signal at a rate of 1.5 Gb/s for 100 meters or more, opticalfiber transmission is essentially used. At present, as shown in FIG. 1,optical fiber transmission and an electrical switcher are used. In FIG.1, reference numeral 101 denotes an electric-optic (E/O) converter forconverting an input serial digital signal into an optical signal,reference numeral 102 denotes an optical fiber for transmitting theoptical signal sent from the E/O converter 101, reference numeral 103denotes an opto-electric (O/E) converter for converting the opticalsignal received from the optical fiber 102 into an electric signal(serial digital signal), reference numeral 104 denotes an electricalswitcher for switching the serial digital signal, reference numeral 105denotes an E/O converter for converting the serial digital signal outputfrom the electrical switcher 104 into an optical signal, referencenumeral 106 denotes an optical fiber for transmitting the optical signalsent from the E/O converter 105, and reference numeral 107 denotes anO/E converter for converting the optical signal received from theoptical fiber 106 into an electric signal (serial digital signal).

[0006] In such a conventional signal transmission/distribution system,the O/E converters 103, the O/E converter 105 and the electricalswitcher 104 are necessarily located on the optical fiber transmissionpath. Therefore, the system becomes disadvantageously complicated. If anoptical switcher enabling one-to-N broadcasting mode connection isprovided, transmission and switching can be accomplished optically, andthus, the system can be simplified and the cost can be reduced.

SUMMARY OF THE INVENTION

[0007] The present invention has been devised to solve such a problem.Accordingly, an object of the present invention is to provide an opticalswitcher capable of sending incident light on one input port to anyplurality of output ports.

[0008] An optical switcher according to the present invention comprises:input ports (2 ₁-2 _(m)) disposed on extensions of m input optical paths(m being 2 or greater natural number); output ports(4 ₁-4 _(n)) disposedon extensions of n output optical paths (n being 2 or greater naturalnumber); and movable switch mirrors (3 ₁₁-3 _(mn)), disposed atintersections of the m input optical paths and the n output opticalpaths, for switching between the input optical paths and the outputoptical paths, in which the movable mirrors are translucent mirrors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] This above-mentioned and other objects, features and advantagesof this invention will become more apparent by reference to thefollowing detailed description of the invention taken in conjunctionwith the accompanying drawings, wherein:

[0010]FIG. 1 shows a configuration of a conventional signaltransmission/distribution system used in a broadcast station.

[0011]FIG. 2 is a perspective view of an optical switcher of a firstembodiment according to the invention;

[0012]FIG. 3 illustrates broadcasting mode connection by the opticalswitcher shown in FIG. 2;

[0013] FIGS. 4(a) and 4(b) show movement of translucent switch mirrorsapplied to the optical switcher shown in FIG. 2;

[0014]FIG. 5 shows a driving circuit arrangement applied to the opticalswitcher shown in FIG. 2;

[0015]FIG. 6 is a plain view of an optical switcher of a secondembodiment according to the present invention;

[0016]FIG. 7 shows a sectional view in an A-A′ axis illustrated inFIG.6;

[0017]FIG. 8 shows a sectional view in a B-B′ axis illustrated in FIG.6.

[0018] FIGS. 9(a)-9(d) show producing processes applied to a firstsubstrate in the A-A′ and B-B′ axes to produce the optical switcher ofthe second embodiment;

[0019] FIGS. 10(a) and 10(b) show producing processes applied to asecond substrate in the B-B′ axis to produce the optical switcher of thesecond embodiment;

[0020]FIG. 10(c) shows a junction process of the first and secondsubstrates in the B-B′ axis to produce the optical switcher of thesecond embodiment; and

[0021]FIG. 10(d) shows a completed state in the B-B′ axis of the opticalswitcher of the second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] [First Embodiment]

[0023] Referring to FIG. 2 showing a perspective view of an opticalswitcher of the first embodiment according to the invention and FIG. 3illustrating broadcasting mode connection in the optical switcher ofFIG. 2, the optical switcher has a plurality of outputs and enables theone-to-N broadcasting mode connection (N being a natural number). In theoptical switcher in FIG. 2, for example, incident light on the i-thinput is to be sent to any plurality of outputs, specifically, the j-th,k-th and l-th outputs.

[0024] As shown in FIG. 2, the optical switcher according to theinvention comprises m input optical fibers 1 ₁-1 _(m) (m being 2 orgreater natural number), input collimator lenses 2 ₁-2 _(m) disposed atm input ports associated with the input optical fibers 1 ₁-1 _(m),respectively, m-by-n translucent switch mirrors 3 ₁₁-3 _(mn) (n being 2or greater natural number), m-by-n drive mechanisms each composed of apower source, such as a piezoelectric actuator that is displaceddepending on an external control signal, and transmission means fortransmitting the displacement of the power source to the associated oneof the translucent mirrors 3 ₁₁-3 _(mn) to cause the same to rotate,output collimator lenses 4 ₁-4 _(n) disposed at n output ports, n outputoptical fibers 5 ₁-5 _(n), input collimator lenses 2 ₁-2 _(m),translucent switch mirrors 3 ₁₁-3 _(mn), and a base 6 on which the drivemechanisms and the output collimator lenses 4 ₁-4 _(m), are mounted.

[0025] Each of the translucent switch mirrors 3 ₁₁-3 _(mn) is providedwith its own drive mechanism. The drive mechanism enables each of theswitch mirrors 3 ₁₁ to 3 _(mn) to assume, independently of others, anupright position in which it reflects part of propagation light incidentfrom the associated input collimator lens (input optical path) towardthe associated output collimator lens or a laid position in which itdoes not intercept the propagation light from the associated inputcollimator lens to allow it to travel straight ahead. The positions ofthe translucent switch mirrors 3 ₁₁-3 _(mn) can be controlled byapplying control signals to their respective drive mechanisms from anexternal control circuit.

[0026] Of course, the switch mirrors 3 ₁₁, 3 ₁₂, 3 ₁₃, . . . , 3 _(1n)are associated with the input collimator lens 1 ₁, the switch mirrors 3_((m−1)1), 3 _((m−1)2), 3 _((m−1)3), . . . , 3 _((m−1)n) are associatedwith the input collimator lens 1 _(m−1), the switch mirrors 3 _(m1), 3_(m2), 3 _(m3), . . . , 3 _(mn) are associated with the input collimatorlens 1 _(m), the switch mirrors 3 ₁₁, 3 ₂₁, 3 ₃₁, . . . , 3 _(m1) areassociated with the output collimator lens 4 ₁, the switch mirrors 3 ₁₂,3 ₂₂, 3 ₃₂, . . . , 3 _(m2) are associated with the output collimatorlens 4 ₂, and the switch mirrors 3 _(1n), 3 _(2n), 3 _(3n), . . . , 3_(mn) are associated with the output collimator lens 4 _(n).

[0027] Now, referring to FIG. 1, an operation of the optical switcheraccording to this embodiment will be described in detail. For example,an optical signal input via the input optical fiber 1 _(m) is convertedinto parallel light by the input collimator lens 2 _(m) to propagate ina space. If the switch mirror 3 _(m1) is in the upright position, thepropagation light is reflected by the switch mirror 3 _(m1) toward theoutput collimator lens 4 ₁, absorbed into the output collimator lens 4₁, and then sent (coupled) to the output optical fiber 5 ₁.

[0028] If the switch mirror 3 _(m1) is in the laid position, thepropagation light travels straight ahead without being reflected towardthe output collimator lens 4 ₁. In this way, the optical signal inputvia the input optical fiber 1 _(m) can be switched to the output opticalfiber 5 ₁ by controlling the rotation angle of the switch mirror 3_(m1).

[0029] Similarly, the optical signal input via the input optical fiber 1_(m) can be switched to the output optical fibers 5 ₂-5 _(n) bycontrolling the rotation angles of the switch mirrors 3 _(m2)-3 _(mn),respectively. The operation described so far is the same as that ofconventional optical switchers and the switch mirrors 3 ₁₁-3 _(mn) havebeen assumed to be total reflection mirrors. However, according to thisembodiment, the switch mirrors 3 ₁₁-3 _(mn) are translucent mirrors(half mirrors). Consequently, according to this embodiment, the one-to-Nbroadcasting mode connection can be realized. Now, an example of theone-to-N broadcasting mode connection will be described with referenceto FIG. 1.

[0030] For example, an optical signal input via the input optical fiber1 _(m−1) is converted into parallel light by the input collimator lens 2_(m−1) to propagate in a space. If the switch mirror 3 _((m−1))is in theupright position, part of the propagation light is reflected by theswitch mirror 3 _((m−1)1) toward the output collimator lens 4 ₁ and sentto the output optical fiber 5 ₁ through the output collimator lens 4 ₁.

[0031] The remaining part of the propagation light, which has passedthrough the switch mirror 3 _((m−1)1), travels straight ahead and, ifthe switch mirror 3 _((m−1)2) is in the upright position, is partiallyreflected by the switch mirror 3 _((m−1)2) toward the output collimatorlens 4 ₂ and sent to the output optical fiber 5 ₂ through the outputcollimator lens 4 ₂. The remaining part of the propagation light, whichhas passed through the switch mirror 3 _((m−1)2), travels straight aheadand, if the switch mirror 3 _((m−1)n) is in the upright position, isreflected by the switch mirror 3 _((m−1)n) toward the output collimatorlens 4 _(n) and sent to the output optical fiber 5 _(n) through theoutput collimator lens 4 _(n).

[0032] Similarly, the optical signal input via the input optical fiber 1_(m−1) can be switched to the output optical fibers 5 ₁-5 _(n) bycontrolling the angles of the switch mirrors 3 _((m−1)1)-3 _((m−1)n) onthe optical path, respectively, in any one-to-N broadcasting mode.Furthermore, according to this embodiment, a translucent switch mirrorlocated nearer the input collimator lenses 2 ₁-2 _(m) has a highertransmittance. In other words, a translucent switch mirror locatednearer the input collimator lenses 2 ₁-2 _(m) has a lower reflectance.This transmittance/reflectance arrangement generally can reducevariations in the powers of the optical outputs in the one-to-Nbroadcasting mode switching.

[0033] In the first embodiment, the translucent switch mirrors 3 ₁₁-3_(m) have been described as rotary type switch mirrors capable ofassuming two, upright and laid, positions, as shown in FIG. 4(a).Alternatively, as shown in FIG. 4(a), the translucent switch mirror maybe a linear type switch mirror that is moved linearly between a positionin which it reflects part of propagation light incident from theassociated input collimator lens toward the associated output collimatorlens and a position in which it allows the propagation light to travelstraight ahead without interception. For driving the mirrors 3, drivingmechanism 3 a such as piezoceramics is applied to each of the mirror 3.

[0034]FIG. 5 shows driving circuit arrangement. In GIG. 5, a controller7 delivers driving signals for each of the driving mechanism 3 aarranged at each of cross points in the optical switch matrix module 8.If piezoceramics is applied as the driving mechanism 3 a, the controller7 supplies certain voltages to the piezoceramics though amplifiers.

[0035] [Second Embodiment]

[0036] Furthermore, the base 6 and the translucent switch mirrors 3 ₁₁-3_(mn) can be implemented as a microelectro-mechanical system (MEMS) byforming them in a silicon substrate by a semiconductor process.Hereinafter, a second embodiment according the present invention formedin a silicon substrate will be described with reference to the FIGS. 6,7, and 8. In FIG. 6 showing a plain view of the second embodiment, atranslucent mirror plate 3′, springs 11 and projecting supports 13 aremade of the same substrate of polySilicon. As shown in FIGS. 7 and 8respectively showing sectional views in A-A′ and B-B′ axes of FIG. 6,the mirror plate 3′ and springs 11 are supported by the supports 13 andpositioned above a substrate 9 of Silicon (Si). In the substrate 9,trench 14 is formed and its surface is covered by SiN deposition.Further, metal material such as aluminum (Al) 12 is deposited on a partof the trench wall as shown in FIG. 7 and thus the mirror plate 3′ canbe rotated in the trench 14 by electrostatic attraction between themetal material 12 and the mirror plate 3′ when a voltage is supplied tothe metal material 12. To supply the voltage, a metal wiring pattern 12′is also arranged on the substrate 9. In the second embodiment,transmittance of the mirror plate 3′ can be controlled by thickness ofthe mirror plate 3′, for example.

[0037] FIGS. 9(a)-9(d) and FIGS. 10(a)-10(d) show producing processes ofthe optical switcher of the second embodiment. As shown in FIGS. 9(a)and 9(b), the trench 14 is produced in the Si-substrate 9 (first wafer)by RIE (Reactive Ion Assisted Etch) dry etching and a projecting portionis formed on the substrate 9 by the RIE dry etching. Further, as shownin FIG. 9(c), the SiN is deposited on the substrate 9 and after this, asshown in FIG. 9(d), the metal material 12 on the part of the trench walland the wiring pattern 12′ are arranged on the substrate 9. Next, toproduce the mirror plate 3′, spring 11 and support 13, another SOI(Silicon on Insulator) substrate (second wafer) shown in FIG. 10(a) isprepared. As shown in FIG. 10(b), the patterns corresponding to themirror plate 3′, spring 11 and support 13 are produced in thepoiysilicon layer of 10 m by silicon RIE etching. After this, as shownin FIG. 10(c) the first wafer and second wafer are bonded by heattreating at 1200 C. Finally, the layers of Si(500 m) and SiO₂(0.5 m) ofFIG. 10(c) are removed by the RIE etching.

[0038] Furthermore, according to the present invention, an optical fiberarray may be used as the input optical fibers 1 ₁-1 _(m) and the outputoptical fibers 5 ₁-5 _(n) and a microlens array may be used as the inputcollimator lenses 2 ₁-2 _(m) and the output collimator lenses 4 ₁-4_(n).

[0039] According to this invention, by using the translucent mirrors asthe movable switch mirrors in the m by n matrix, the optical switchercapable of sending incident light on one input port to any plurality ofoutput ports can be provided. Thus, the optical switcher enabling theone-to-N broadcasting mode connection can be provided, and the systemcan be simplified and the cost can be reduced compared with theconventional signal transmission/distribution system including thephotoelectric converters and the electrical switcher.

[0040] Furthermore, since a movable switch mirror located nearer theinput port has a higher transmittance, the variations in the powers ofthe optical outputs appearing when incident light on one input port issent to any plurality of output ports can be reduced.

What is claimed is:
 1. An optical switcher, comprising: input portsdisposed on extensions of m input optical paths (m being 2 or greaternatural number); output ports disposed on extensions of n output opticalpaths (n being 2 or greater natural number); and movable translucentswitch mirrors, disposed at intersections of the m input optical pathsand the n output optical paths, for switching between said input opticalpaths and said output optical paths.
 2. The optical switcher accordingto claim 1, wherein a movable switch mirror located nearer said inputports has a higher transmittance.
 3. The optical switcher according toclaim 1, wherein the movable translucent switch mirror comprises amicroelectro-mechanical arrangement.
 4. The optical switcher accordingto claim 3, wherein said microelectro-mechanical arrangement includes:substrate; a plurality of trenches arranged in said substrate, theplurality of trenches being allocated in matrix manner; translucentplates disposed above each said trenches, said translucent plates beingcapable of rotating in said trenches; and driving means for rotatingsaid translucent plates.
 5. The optical switcher according to claim 4,wherein said microelectro-mechanical arrangement further includes metalmaterial deposited on a part of wall of said trenches and saidtranslucent plate is rotated by electrostatic attraction between saidtranslucent plate and said metal material.
 6. The optical switcheraccording to claim 4, wherein said microelectro-mechanical arrangementfurther includes supporting means for supporting said translucent plate.